A client station (STA) can operate in a wireless local area network (WLAN) by communicating with an access point (AP). The communication signals between the STA and the AP can include an uplink and a downlink signal. The downlink signal from the AP may also be called the link signal, or simply, the link. The quality of the uplink and downlink signals may vary with time, STA position with respect to the currently selected AP, weather, and other factors.
The STA may supplant the current AP with a new AP as needed. The act of switching to communicate with a new AP may be called roaming. Roaming in WLAN STAs may be distinguished from network roaming in cellular networks in which a user equipment (UE), such as a cellular telephone, can select and communicate with either a new base station (BS) within a current cellular network or a new cellular network. In a cellular network, the BS may assist or command the UE to roam to a new base station.
In a WLAN, an STA may roam without receiving assistance or roaming commands from the AP. An STA may prepare to roam by scanning the link signals from candidate APs. The STA may scan the links while performing other tasks, such as uplinking a signal, updating internal information, or executing other tasks. The STA may roam to a new AP based on the scan, albeit with some latency. The STA may also periodically scan during normal operations. The periodic scanning process can be called background scanning. Background scanning can prepare the STA to roam to a new AP quickly.
Background scanning can consume STA resources and can reduce the throughput or information transfer rate between the STA and the currently selected AP. The demand on STA resources, throughput reduction, and other performance costs can depend on the duration of each scan, the frequency of scans, the probability that a new AP actually offers a better link signal, and other factors.